How to verify that the average is really a simple calculation?Thank you, joriki. The most enlightening part for me is: "[...] the question is then how to tell whether all the possible matches have the same probability of being drawn in the second draw "even though" two balls have already been removed. This is clearly the case, since the balls that were removed were themselves picked randomly with uniform distribution, so there's nothing there that could break the symmetry between the teams."